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Morais D.M.S.,Aeronautics Technical Institute | Panasiewicz J.,Aeronautics Technical Institute | Panasiewicz J.,National Institute for Space Research | Pacheco G.M.,Aeronautics Technical Institute
Progress in Electromagnetics Research Symposium | Year: 2015

This paper describes the behavior of a microwave external modulation link composed of: optical and radio frequency sources, Mach-Zehnder modulator (MZ), optical fiber and photodetector. The electro-optical circuit modulates the RF signals and transmits them to the detector through the optical fiber. The main contribution of this paper lies on the different approach to the system analysis; we consider an off-quadrature biased MZM. By extending the mathematical model found in the literature for the case of different bias voltages, we compute a few performance parameters of the system like Gain and SFDR. For computing those parameters we use a custom made program written in the MATLAB environment. In addition to the system's characterization and insights on its off-quadrature operation, another contribution of this article is the model validation. We assembled the electro-optical circuit and measured some performance parameters for different values of bias voltages. By comparing the experimental results with the theoretical ones, we validated the model. Finally, we also consider the applications for microwave signals distribution by optical fiber links. Source

Panasiewicz J.,National Institute for Space Research | Panasiewicz J.,Aeronautics Technical Institute | Morais D.M.S.,Aeronautics Technical Institute | Pacheco G.M.,Aeronautics Technical Institute
Progress in Electromagnetics Research Symposium | Year: 2015

This paper addresses the subject of the satellite payload signal transmission and the digital-microwave link. Usually, the carrier modulation data transmitter (DT) employs in-phase (I) and quadrature-phase (Q) processing to achieve phase shift keying (M-PSK). Typically, this I/Q processing is obtained by multiplying a low-frequency reference signal. Such systems usually have many stages of multipliers, amplifiers and filters. As a result the microwave transmitter is complicated, bulky and costly. The results presented are based on a photonic circuit that achieves QPSK modulation directly at the microwave frequency carrier. The QPSK modulation was performed using a carrier frequency of 2GHz and 2Mbps I/Q signal from a pattern generator using a photonic circuit with a pair of Mach-Zehnder optical modulators arranged in a parallel configuration. The source of the photonic circuit is a DFB diode laser with a wavelength equal to 1550 nm. The modulated optical signal direct detection comes from an InGaAs photo detector. The optical modulator circuit output can be directly connected to the high power amplifier (HPA) and the transmission antenna. The resulting system enables one to achieve a microwave data transmitter with a reduced mass and volume, further lowering power consumption. These achievements are very important for spacecraft engineering teams during the conception of the satellite payloads when starting a new satellite project. Gamma radiation and thermal effects of the space environment are also discussed. Source

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